Measuring and Manipulating how Proteins Control their Net Charge: Redox Enzymes, Crowded Enzymes, and Aggregated Proteins.

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With the support from the Chemistry of Life Processes Program in the Division of Chemistry, Professor Bryan F. Shaw from Baylor University will investigate new ways to measure and manipulate the electrostatic properties of proteins. In contrast to other properties of proteins, the net electrostatic charge (denoted “Z”) is not typically measured or studied. Consequently, it is not known how or by what magnitude the net charge of a protein changes when electrons are transferred to or from a protein and how molecular crowding within a cell may affect this change. This knowledge gap may limit the understanding of how living cells work. Dr. Shaw’s research group is using capillary electrophoresis to measure how the net charges of different proteins change during protein crowding and electron transfer. The Shaw research team will evaluate how the electrostatic properties of proteins may be controlled or altered by small molecules or mutations, to ultimately affect catalysis and protein self-assembly. In parallel with these research activities, new tools will be developed, tested, and implemented, to make chemical imagery and data accessible to college students with blindness. Dr. Shaw’s research team converts 2D data and imagery into “lithophane” format. Lithophanes are tactile graphics that glow with video-like resolution when held up to ambient light. Persons with blindness can visualize the lithophane data by touch (tactile sensing), whereas sighted persons can visualize the exact same lithophane data using eyesight. This Lithophane Data Format (LDF) promotes diversity and inclusion by enabling data sharing between sighted and blind scientists.The proposed research focuses on the magnitude of the change in net charge of a protein upon proton-coupled electron transfer (PCET), as opposed to electron transfer that is not coupled to proton transfer. Experiments will be performed to identify which amino acid residues in certain metalloproteins affect the change in net charge during these redox processes. The proposed research will also measure how the activity of an enzyme (e.g., RNase) is affected by the net charge of a crowded protein neighbor at distances up to 8 Å. Investigating how the catalytic activity of enzymes can be altered by the net charge of its nearest crowded neighbor has the potential to improve our understanding of cellular protein localization and function. The research also involves the design and synthesis of small molecules that electrostatically disrupt coulombic interactions between proteins and biological surfaces. The research has potential impact in biochemistry, including enzymology, bioinorganic chemistry, and protein biophysics because it examines fundamental electrostatic effects upon protein-based electron transfer, protein crowding and self-assembly, and upon catalysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.